It is known in optical telecommunications to multiplex the data to be transmitted in order to transmit a largest possible volume of data via an optical waveguide. One possibility for this consists in transmitting information with a plurality of wavelengths independently and simultaneously via one waveguide. In this case, it is necessary, at the transmission end, to combine the signals from the various light sources by means of an optical multiplexer into an optical waveguide and, at the receiver end, to divide the signals having different wavelengths from the incoming waveguide into individual channels for separate detection by means of an optical demultiplexer.
In order to realize a multiplexing or demultiplexing, it is known from EP A 0 877 264 to separate the individual wavelengths by means of interference filters. By virtue of a high number of interference layers, the interference filters generate very steep spectral edges between transmission and reflection of different wavelengths. Only a specific wavelength is transmitted by the interference filters in this case, while the other wavelengths are reflected. By cascading such filters with individually different spectral transmission positions, it is possible to effect a selection or combination of a multiplicity of wavelength channels. The use of interference filters is extremely effective particularly in the case of relatively large wavelength separations of 10 nm or more between the individual channels.
WO 02/16987 A1 describes an optoelectronic assembly for multiplexing and/or demultiplexing optical signals having a monolithic multiplex body and two optical imaging systems for coupling light beams into or out of the multiplex body. A parallel light beam which enters the multiplex body at an acute angle via a single-channel interface body is multiply reflected back and forth between the two parallel surfaces, the light beam being coupled out at wavelength-selective mirror areas in each case with a wavelength component.
WO 03/012505 A1 discloses an apparatus for multiplexing and/or demultiplexing optical signals having a plurality of wavelengths, in which optical signals in waveguides impinge on a wavelength-selective filter in each case at different angles, optical signals having only a specific wavelength being coupled in or out for each angle.
EP 1 004 907 A2 and WO 01/02887 A1 disclose using a common body having a plurality of lenses for coupling in and out parallel beams having a different wavelength. As a result, a reduction of the parts is achieved, but a very high precision must be ensured. Moreover, components having the high complexity required can only be produced in plastic, so that the properties of the plastics used, such as the thermal and optical behavior thereof, limit the practical applications.